In accidents involving motor cyclists wearing a crash helmet there is a danger of injuries in the region of the cervical vertebrae if the head is thrust backwards, as well as in the region of the breast bone or collar bone if the head is wrenched forward or side-ways. For example, when the head is turned upwardly and rearwardly the portion of the spine formed by the cervical vertebrae bows rearwardly. At the limit of this bowing movement the vertebrae stop and lock and forces applied to the head are exerted on the vertebrae. If these are too great the vertebrae are displaced or damaged causing injuries which may be serious and even death. Furthermore, there is a danger of the lower rim of the rear of the helmet being forced against the back of the neck. For this reason, a number of crash helmets have an area cut out at the nape of the neck so as to prevent the rear lower rim of the helmet from acting on the region of the cervical vertebrae. The freedom of the head to move backwards is increased by this measure, so that particularly in the event of a crash at high speed, the head with the helmet is displaced backwards. In this case, the risk of the cervical portion of the spine being bowed excessively and of the cervical vertebrae from being separated and breaking, causing damage to the spinal cord, is increased.
Various proposals have been made for reducing these dangers, for example the use of a neck-engaging pad, but no adequate solution has hitherto been found.